$ C = \left[\begin{array}{rrr}0 & 2 & 1 \\ 1 & 0 & 2 \\ 1 & 2 & 0\end{array}\right]$ What is $ C^{-1}$ ?
$ = \left[\begin{array}{rrr}-\frac{2}{3} & \frac{1}{3} & \frac{2}{3} \\ \frac{1}{3} & -\frac{1}{6} & \frac{1}{6} \\ \frac{1}{3} & \frac{1}{3} & -\frac{1}{3}\end{array}\right]$